a: \(=y^2+32>=32\)
Dấu = xảy ra khi y=0
b: \(=2x^2-x+2x-1\)
\(=2x^2+x-1\)
\(=2\left(x^2+\dfrac{1}{2}x-\dfrac{1}{2}\right)\)
\(=2\left(x^2+2\cdot x\cdot\dfrac{1}{4}+\dfrac{1}{16}-\dfrac{9}{16}\right)\)
\(=2\left(x+\dfrac{1}{4}\right)^2-\dfrac{9}{8}>=-\dfrac{9}{8}\)
Dấu '=' xảy ra khi x=-1/4